What is the difference between the blackness of a Black Hole and the blackness of a Black Body? 
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*Light cannot escape the gravitational pull of the black hole and hence the 'black hole' is black.

*Any object that is black in color, absorbs all wavelengths of light and reflects none. So it appears black.
Could someone explain the key difference between these two phenomena ?
 A: A black body is a system that does not reflect photons. A black body can only emit photons, which is often fabricated as a hot cavity with a small hole. A razor blade can also approximate a black body if the sharp edge is smaller than the wavelength of photons of interest and is at a temperature so short wavelength photons are not significantly present. A black body then has a small reflectivity relative to the emissivity $r(\lambda)~<<~\epsilon(\lambda)$ for wavelengths of interest. An ideal black body has zero reflectivity for all wavelengths.
A black hole absorbs anything, including photons that reach it. It has zero reflectivity. Even if a photon entering a black hole reaches a mirror that is right at the event horizon, since the mirror has $z~\rightarrow~\infty$ the photon is not reflected back. The black hole also interacts with the quantum vacuum, in that virtual quanta across the horizon becomes an entangled pair of a negative energy quanta entering the black hole and a positive energy quanta that escapes to "infinity." This is a bit of heuristic, but it helps us see that a black hole losses a bit of mass and that mass escapes. The low energy form of this is of course photons, which have zero mass gap. As a result a black hole is about the most ideal black body in the universe. 
